The object of this research is to learn more about the mechanisms underlying both normal eye movement control and human oculomotor disorders. The research strategy is to make quantitative measurements of oculomotor function in both humans and monkeys and to use systems approaches to interpret findings. The latest techniques for measuring and analyzing eye motion around all three axes and imaging the eye muscles will be used. The focus is on mechanisms that maintain oculomotor accuracy with emphasis on binocularity and compensation for translational head motion. The study of adaptive mechanisms will be emphasized--specifically the capability to maintain eye alignment around all axes (horizontal, vertical, torsion) of eye rotation during steady fixation and during head motion. The superior oblique (SO) palsy model will be used to investigate adaptation to vertical and torsional misalignment, and the results correlated with orbital MRI. The role of the cerebellum in the immediate and long-term adaptive control of these mechanisms will be explored. Parallel and complementary human and monkey experiments are proposed. These results will provide new information about adaptive control of eye alignment relative to strabismus and eye movements that compensate for head motion.